In the third-season finale, the Reagans go after a gang leader who killed someone close to them, and Danny works an angle involving the gang leader's girlfriend. Meanwhile, a second crisis occurs and unnerves Frank.

In the fourth series opener, a cop killer is arrested, but Erin drops the charges against the suspect due to lack of evidence. Following her legal actions, friction results between her and the police officers in her family.

A mob lawyer gets shot and Frank is almost killed after the two of them dine together. Elsewhere, Danny serves on jury duty and finds himself disagreeing with all of his fellow jurors while deliberating a murder case.

A convicted rapist-murderer is released from prison because of a faulty DNA test and he targets a member of the Reagan family for revenge. Erin tries to get a victim who escaped from the killer to testify against him, but she refuses to do so even though h (more…)A convicted rapist-murderer is released from prison because of a faulty DNA test and he targets a member of the Reagan family for revenge. Erin tries to get a victim who escaped from the killer to testify against him, but she refuses to do so even though her testimony would send him back to prison.

A doorman at a popular nightclub is murdered. The investigation reveals the victim was heavily in debt because of gambling. The sexy nightclub owner flirts with Danny during the probe and it causes Linda to worry about whether Danny will stray. Meanwhile (more…)A doorman at a popular nightclub is murdered. The investigation reveals the victim was heavily in debt because of gambling. The sexy nightclub owner flirts with Danny during the probe and it causes Linda to worry about whether Danny will stray. Meanwhile, Frank learns that an old friend on the force may be covering up crimes in an attempt to gain a promotion.

Danny and Jackie investigate the murder of a high-end escort after the victim's body is found in the East River just hours after she phoned Danny for help. Meanwhile, Frank reopens a cold case from 25 years ago when a missing boy's remains are discovered i (more…)Danny and Jackie investigate the murder of a high-end escort after the victim's body is found in the East River just hours after she phoned Danny for help. Meanwhile, Frank reopens a cold case from 25 years ago when a missing boy's remains are discovered in the basement of a building near where he vanished.

A Russian mobster's son is gunned down at his engagement party and suspects soon become mob targets. Danny tries to solve the case before more bodies pile up. Meanwhile, Erin becomes involved in a high-profile corruption case that is connected to the mayor (more…)A Russian mobster's son is gunned down at his engagement party and suspects soon become mob targets. Danny tries to solve the case before more bodies pile up. Meanwhile, Erin becomes involved in a high-profile corruption case that is connected to the mayor's office.

A girl is kidnapped and held for ransom. The abductor demands £5 million in diamonds or he will kill her. The investigation leads Danny and Jackie to suspect the girl's boyfriend is responsible. Meanwhile, Frank looks into charges that a cleaning lady's s (more…)A girl is kidnapped and held for ransom. The abductor demands £5 million in diamonds or he will kill her. The investigation leads Danny and Jackie to suspect the girl's boyfriend is responsible. Meanwhile, Frank looks into charges that a cleaning lady's son was involved in an armed robbery.

A 16-year-old girl is murdered at a hotel where a debutante ball is taking place and her body is dumped in an alley. Nicky rides along with Danny to the crime scene and glimpses the victim, which leads to recurring nightmares. Meanwhile, Frank is pressured (more…)A 16-year-old girl is murdered at a hotel where a debutante ball is taking place and her body is dumped in an alley. Nicky rides along with Danny to the crime scene and glimpses the victim, which leads to recurring nightmares. Meanwhile, Frank is pressured by the mayor's new publicist to be the subject of several magazine-cover stories that will play him up as a hero.

Baez's estranged brother becomes a murder suspect in a case she and Danny are investigating. Elsewhere, claims of police brutality are made against a dog in the K9 unit; and Henry suspects that his pal's widow might be responsible for her spouse's death.

Danny and Baez work on a bombing case, but the community affected is not very cooperative. Elsewhere, a man assaults a cop who got too intensive with his line of questioning, and Frank must deal with the repercussions.

Danny's wife is kidnapped to prevent him from testifying against a Peruvian drug lord who's on trial for a murder that Danny witnessed. The investigation reveals that the suspect has a history of torturing and killing potential witnesses and that there is (more…)Danny's wife is kidnapped to prevent him from testifying against a Peruvian drug lord who's on trial for a murder that Danny witnessed. The investigation reveals that the suspect has a history of torturing and killing potential witnesses and that there is a mole in the police department who is feeding him information.

Linda's runway-model niece collapses during a fashion show and a former supermodel dies a few seconds later at the event. The investigation reveals both were poisoned. Meanwhile, the Reagans' family priest is accused of sexual misconduct by a woman and is (more…)Linda's runway-model niece collapses during a fashion show and a former supermodel dies a few seconds later at the event. The investigation reveals both were poisoned. Meanwhile, the Reagans' family priest is accused of sexual misconduct by a woman and is being reassigned to South America, even though he claims he is innocent.

A tourist is robbed and gunned down outside a popular Lower East Side restaurant and the press sensationalize the story to make it seem as if crime is on the rise in the city, which infuriates Frank. Meanwhile, Erin feels responsible when a woman is killed (more…)A tourist is robbed and gunned down outside a popular Lower East Side restaurant and the press sensationalize the story to make it seem as if crime is on the rise in the city, which infuriates Frank. Meanwhile, Erin feels responsible when a woman is killed by a felon she couldn't put away in court.

Family friends of the Reagans' are murdered and their drug-addicted son is the chief suspect. Meanwhile, Jamie's gun is stolen and he believes he is being set up for investigating the secretive Blue Templar police organization.

The first series concludes with Frank attempting to take down the secretive Blue Templar police organization and discover who killed his son, after a drug bust exposes some dirty cops. Meanwhile, Jamie rescues a woman from kidnappers and begins to fall for (more…)The first series concludes with Frank attempting to take down the secretive Blue Templar police organization and discover who killed his son, after a drug bust exposes some dirty cops. Meanwhile, Jamie rescues a woman from kidnappers and begins to fall for her.

The second series begins with a supporter of the new mayor being murdered and the mayor asking Frank to spin the story so it looks like a random act of violence. Meanwhile, Jamie gets his first undercover assignment.